Auxiliary Power Unit - Spacecraft

Spacecraft

The Space Shuttle APUs provided hydraulic pressure. The Space Shuttle had three redundant APUs, powered by hydrazine fuel. They functioned during powered ascent, re-entry, and landing. During ascent, the APUs provided hydraulic power for gimballing of Shuttle's engines and control surfaces. During landing, they powered the control surfaces and brakes. Landing could be accomplished with only one APU working. On STS-9, two of Columbia's APUs caught fire, but the craft landed successfully.

Read more about this topic:  Auxiliary Power Unit